Magnetotransport ofν=3/2composite fermions under periodic effective magnetic-field modulation

Abstract

We report magntetotranport measurements around a filling factor $\ensuremath{\nu}=\frac{3}{2}$ of two-dimensional electron gas under weak unidirectional periodic potential modulation. Composite fermions (CF's) at $\ensuremath{\nu}=\frac{3}{2}$ which are the electron-hole conjugate of $\ensuremath{\nu}=\frac{1}{2}$ CF's, show positive magnetoresistance (PMR) and oscillatory magnetoresistance---commensurability oscillation (CO)---for a modulation period of $a=92\mathrm{nm}.$ Minima of the CO occur at the positions expected for commensurability with effective magnetic-field modulation, and are consistent with the field-dependent Fermi wave number ${k}_{F}$ resulting from field-dependent density of the $\ensuremath{\nu}=\frac{3}{2}$ CF's. The positions are consistent with ${k}_{F}$ for fully spin-polarized CF's, except for one dip which is better explained by a fully spin-unpolarized ${k}_{F},$ smaller by factor $\sqrt{2}$ than its spin-polarized counterpart. With the introduction of in-plane magnetic field by tilting, the PMR shows unexpected asymmetry: it grows both in its magnitude and extent on the lower-field side, while it shrinks on the higher-field side.